Low Carbon Materials

Question 1

What is Bioconcrete

Answer 1

Environmentally friendly alternative to trad concrete

Adds bacteria to concrete mix to reduce cement content

Self-healing properties

Question 2

What’s added to bioconcrete?

Answer 2

Bacteria
1. Nutrients
2. Calcium ions
3. Microorganisms (precipitate calcium carbonate)

Question 3

Advantages of Bioconcrete

Answer 3

1. Superior durability (longer design life, good for bridges/tunnels/roads)
2. Improved crack resistance
3. CO2 neutral
4. Reduced permeability (good for marine)
5. sometimes higher strength
6. Reduced design life cost
7. Reduced maintenance costs

Question 4

Disadvantages of Bioconcrete

Answer 4

1. Higher cost (double)
2. Low availability of bacteria
3. Potential harm to human health
4. Difficulty maintaining pH for bacteria to survive
5. No definitive method of adding bacteria
6. Microcapsules create planar weaknesses
7. More research needed

Question 5

What is Concrete Reinforced with Bamboo

Answer 5

Bamboo replaces steel, must be coated with bitumen/sand to prevent shrinking/swelling

Question 6

Advantages of concrete reinforced with bamboo

Answer 6

1. Renewable material (rapid regrowth post harvesting)
2. Reduced CO2 consumption (low carbon)
3. Light-weight (ease of constructability)
4. Cheap for locals
5. Simples & cheap harvesting process
6. Readily available

Question 7

Disadvantages of concrete reinforced with bamboo

Answer 7

1. Not significantly cheaper than steel (transport, coating)
2. Requires additional concrete to meet stability, load-bearing requirements
3. Inconsistent tensile strength values
4. Only good for lightweight structures

Question 8

What is timber-concrete composite?

Answer 8

Timber beams & deck form bottom layer with concrete poured on top.
Dowels, rods, screws set into wood & surrounded by concrete are critical connections
compliments concrete’s compression & timber’s tensile resistances

Question 9

Advantages of timber-concrete composite

Answer 9

1. Reduce concrete use
2. Timber has carbon sequestration (smaller carbon emissions)
3. Enhanced thermal performance
4. Good sound insulation
5. Reduced self-weight
6. Superior flexural behaviour

Question 10

Disadvantages of timber-concrete composite

Answer 10

1. Timber requires maintenance (moisture)
2. Resource depletion of timber
3. Lack of well-defined design guidlines & standards
4. Timber’s susceptibility to moisture requires waterproofing & maintenance

Question 11

What is geopolymers

Answer 11

use alkali to activate limestone materials and bind material together
precursor & chemical activator

precursor - aluminosilicate
activator - alkali&water (water glass)

Question 12

Advantages of geopolymer

Answer 12

1. Good fire resistance
2. Good chemical resistance
3. Good adhesion to surfaces e.g. for repairs
4. Prevent reinforcement corrosion compared to Portland cement
5. Low cost
6. upcycling of industrial wastes
7. Low CO2 emission footprint

Question 13

Disadvantages to Geoploymers

Answer 13

1. Requires sealed curing (for early age strength, to avoid cracking and evaporation)
2. Quick setting
3. Low very early-age strength (may need to leave more like 14 days than 1)
4. handling difficulties
5. Water glass (activator) has large carbon emissions, but v.small amount is used

Question 14

Advantages of Recycled concrete aggregate

Answer 14

1. Upcycles construction waste

Question 15

Disadvantages of RCA

Answer 15

1. Complex sorting and preparing aggregate process (extraction, crushing, screening)
2. Rougher surfaces so more energy for mixing
3. More porous
4. may need more water for workability
5. Low strength